Torture at the turn of the bilge

The forward section of the turn of the bilge is a tough cookie. The 10mm plywood needs to be bent and twisted (aka tortured) to conform to a relatively small radius at the E frame while following the water lines. When making the E frame I made the bilge radius quite small knowing it might be a problem, but I wanted to avoid the narrow-nosed variant of the setka I have seen in many other blogs. I prefer my hard chined boats curvy where possible 😉

I tried to minimize the curvature along the water lines by widening the nose and introducing a significant curvature of the bilge piece at the stem to minimize the undevelopability of the piece. As I noted before, The Design is wonderfully vague on the specifics of the forward section so I took all the liberties I felt needed...

First try was to see if the plywood would bend just like that. I clamped the lower edge to the chine log using a beam and I shimmed the sligtly concave middle section to apply a bit more pressure where I could not put a clamp. The board would not budge. It did break though, at the shim, not even where it was being bent. Those pesky forces popping up where you don't expect them...

Second time around I screwed the lower edge with shiny 5mm wide-thread screws (spaced 6cm apart) to make sure the forces were distributed evenly and clamped the whole thing like before. I have put wet towels on the boards to soften them up a bit and slowly started applying pressure.

After 6 hours of slowly inching it in it was done. I will leave the whole thing to air dry under pressure and will keep the plates clamped for at least a few days while I'm doing other stuff.
The other stuff was, and will be for the next couple of days the oh so glorious cleanup of the fillets, cleaning them, sanding them, (re-)applying them, not to mention washing them with luke warm water. So many things one can do with one's time.

In most cases it is purely esthetic, but there are a few spots where not enough resin was squeezed out to make a fillet and I'd like to have nicely rounded edges everywhere - easier to clean and less moisture related problems.
ciao.

The lower chine story

In the last post I showed my attempt at steam bending the chine logs - it kinda worked, but only just kind of. The spruce proved super tough and resistant to bending so I had to figure out a way to reduce the internal stresses in the glue joints. Instead of forcing the log into place I decided to glue in an intermediary wedge. In addition, the gluing surface is more than doubled, see pictures below. The cut angles are euivalent to a 12:1 scarf, which should be aok since i'm relying on glued scarf joints in many places of the build.

In order to keep everything lined up I first glued the logs to the stem and the first bulkhead. Afterwards, making sure the center line is kept I glued the logs to the slots in the rest of the frames. Most probably I will only add fasteners at the stem and the transom, I see little reason to break the continuity of the fibers amidship where it matters.

Keeping the log twisted the correct amount with plywood wrenches makes for a pretty easy fit, no need to use fasteners and weaken the stringers.

 Part of the reason the bending process was so challenging was that the stem sagged by 15mm. Or maybe I put it lower to compensate for the fact I cut it a bit short on the deck side and then forgot about it. Anyway, I laminated 2 strips of wood to the logs to compensate for that, restoring the geometry and adding some additional strength to the forward section.

Next step, tomorrow, will be shaping the bottom chines and fine tuning the bevels.
ahoy.

Steam bending the longitudinals (under quarantine)

The lower chine stringers need to be bent and twisted in the bow section, quite dramatically. I couldn't make it work cold and dry so I decided to do some steam bending. Under the French quarantine law I cannot just go to the hardware store (which is closed btw., who knows for how long) so I had to improvise a steaming jig. I found some plastic foil that withstood my home cooked boiling test - same stuff I have covered the floor with), bubble wrap for insulation, some plastic bottles to prevent the foil from collapsing on the planks, a home water cooker and voila, a steaming contraption is born.

Cooking the wood for 2 hours did make it much more pliable. Technically it did let itself be forced to where I needed it to be:

BUT: it did split and check. A little bit. I am not worried though, the fibers did not break, they just separated. I will glue the split, fill in the cracks and it will be good as new. In this section those stringers are not carrying any longitudinal loads, they are there mostly to hold the plating, the chine in that section is at a 45 deg angle (and more) so the stiffness is also generated by the plating geometry. So I'm good.

I'm letting the stringers rest clamped up before I shape and attach them.

 

It has also gotten cold again so I cannot comfortably apply epoxy, which is just as well. The longer the wood sits in the frame the easier it will be to glue it. I ordered some 205 fast hardener to be able to finish the hull in cold weather, it cures in temperatures down to 4 degC. It will take a few days to arrive so I'll probably start shaping the bevels on the upper chine and glue up the 3 last deck beams.
auf widersehen.

Side plating

Once dry fitted the installation procedure is quite straightforward, although, as with everything in this build, quite time consuming. Fitting, surface prep, pre-wet with epoxy, apply thickened epoxy, join, screw in fasteners, install butt blocks, clean up squeeze out, admire result, wrap up in bubble wrap, turn on heating for the night to allow for a healthy epoxy cure.

The sides are, lengthwise, almost covered by 2 sheets of plywood (your mileage may vary, plywood stocks are not all created equal), only a small ~30cm piece needs to be covered in addition. Since I join the sheets using butt blocks (also made of the same plywood) I decided to extend those all the way back to the stern and slot them in with dove tails. (Probably won't hurt, best case scenario the overall joint strength will improve).

 

After everything fits, mark the locations of the frames and stringers, pre-drill holes, apply glue and start attaching the skin to the frame.

 

After a few hundred screws my drill started smoking and stopped working. Miraculously, however, it came back to life the next day.

While the glue is still soft some cleanup is required, cleaning off fully cured epoxy is no fun.

I managed to make small fillets in most places, it is mostly about preventing moisture ingress rather than structural reinforcement, but I will probably re-fillet with a slightly larger radius to match the color of the wood anyway.

Many hours later the hull is wrapped in bubble wrap, a heater is placed inside and the curing can go on despite temperatures at night dropping to zero centigrade.

Next step is the bottom longitudinals and the rest of the plating. To be reported on soon.

Materials for glassing the hull

Today a big order arrived containing the materials needed for reinforcing the hull: biaxial glass cloth, resin and fairing compound filler. After much research and deliberation I went with an all West System solution, mostly due to the ample documentation and their reputation. They are maybe a bit more pricey that regular off the shelf stuff, but I could order everything in one go, everything came nicely packaged and, quite important: their resin is easy to use: flows/mixes nicely and comes with metering pumps and everything.
The glass came factory prepackaged in 5m rolls, not folded as often happened when I was buying glass from other suppliers. The plans call for at least 200g/m^2 woven cloth, I went with 300g biaxial, the laminate should be about the same weight due to better glass to resin ratio and be (a lot) stronger. Does the additional strength matter? Probably not, as the design with 200g woven has proven itself and is plenty strong. But the biaxial might be a bit smoother and therefore easier to fair - big question since I never used biax before, probably just wanted to try something new :)

As for actually glassing the hull: I'm not ready yet, working on plating it right now, I'll describe the whole process of plating in a single post once it is done, which should be soon.
until then.